The Future of Computers - Electronic nanocomputers

Due to our fifty years of experience with electronic computing devices, including the extensive research and industrial infrastructure built up since the late 1940s, advances in nanocomputing technology are likely to come in this direction making the electronic nanocomputers appear to present the easiest and most likely direction in which to continue nanocomputer development in the near future.

Electronic nanocomputers would operate in a manner similar to the way present-day microcomputers work. The main difference is one of physical scale. More and more transistor s are squeezed into silicon chips with each passing year; witness the evolution of integrated circuits (IC s) capable of ever-increasing storage capacity and processing power.

The ultimate limit to the number of transistors per unit volume is imposed by the atomic structure of matter. Most engineers agree that technology has not yet come close to pushing this limit. In the electronic sense, the term nanocomputer is relative; by 1970s standards, today's ordinary microprocessors might be called nanodevices.

How it works

The power and speed of computers have grown rapidly because of rapid progress in solid-state electronics dating back to the invention of the transistor in 1948. Most important, there has been exponential increase in the density of transistors on integrated-circuit computer chips over the past 40 years. In that time span, though, there has been no fundamental change in the operating principles of the transistor.

Even microelectronic transistors no more than a few microns (millionths of a meter) in size are bulk-effect devices. They still operate using small electric fields imposed by tiny charged metal plates to control the mass action of many millions of electrons.

Although electronic nanocomputers will not use the traditional concept of transistors for its components, they will still operate by storing components, information in the positions of electrons.

At the current rate of miniaturization, the conventional transistor technology will reach a minimum size limit in a few years. At that point, smallscale quantum mechanical efects, such as the tunneling of electrons through barriers made from matter or electric fields, will begin to dominate the essential effects that permit a mass-action semiconductor device to operate Still, an electronic nanocomputer will continue to represent information in the storage and movement of electrons.

Nowadays, most eletronic nanocomputers are created through microscopic circuits using nanolithography.

Nanolitography

Nanolithography is a term used to describe the branch of nanotechnology concerned with the study and application of a number of techniques for creating nanometer-scale structures, meaning patterns with at least one lateral dimension between the size of an individual atom and approximately 100 nm.

A nanometer is a billionth of a meter, much smaller than the width of a single human hair. The word lithography is used because the method of pattern generation is essentially the same as writing, only on a much smaller scale. Nanolithography is used during the fabrication of leading-edge semiconductor integrated circuits (nanocircuitry) or nanoelectromechanical systems (NEMS).

One common method of nanolithography, used particularly in the creation of microchips, is known as photolithography. This technique is a parallel method of nanolithography in which the entire surface is drawn on in a single moment. Photolithography is limited in the size it can reduce to, however, because if the wavelength of light used is made too small the lens simply absorbs the light in its entirety. This means that photolithography cannot reach the super-fine sizes of some alternate technologies.

A technology that allows for smaller sizes than photolithography is that of electron-beam lithography. Using an electron beam to draw a pattern nanometer by nanometer, incredibly small sizes (on the order of 20nm) may be achieved. Electron-beam lithography is much more expensive and time consuming than photolithography, however, making it a difficult sell for industry applications of nanolithography. Since electron-beam lithography functions more like a dot-matrix printer than a flash-photograph, a job that would take five minutes using photolithography will take upwards of five hours with electron-beam lithography.

New nanolithography technologies are constantly being researched and developed, leading to smaller and smaller possible sizes. Extreme ultraviolet lithography, for example, is capable of using light at wavelengths of 13.5nm. While hurdles still exist in this new field, it promises the possibility of sizes far below those produced by current industry standards. Other nanolithography techniques include dip-pen nanolithography, in which a small tip is used to deposit molecules on a surface. Dip-pen nanolithography can achieve very small sizes, but cannot currently go below 40nm.